A. Field of the Invention
The present invention relates to a flywheel assembly, and in particular to a flywheel assembly having a flexible plate for damping a bending vibration transmitted from a crankshaft of an engine.
B. Description of the Background Art
Combustion energy from an engine is converted into a torque by the arrangement of a crankshaft in the engine in a manner well known in the art. The torque is transmitted to a flywheel, and is further transmitted to a transmission via a clutch.
The combustion process within the engine is such that the energy transmitted to the crankshaft exerts a bending force on the crankshaft. Bending of the crankshaft causes a vibration of a flywheel attached to an end of the crankshaft. A counter-force thereof is transmitted to an engine block, and is further transmitted to a body of a vehicle via an engine mount to vibrate the body. This causes noises during acceleration of the vehicle.
In order to reduce such noises during acceleration, it is necessary to reduce vibrations of the flywheel. For this purpose, flywheel assemblies have also been employed that are coupled to an end of a crankshaft via a flexible plate. The flexible plate has a high rigidity in the rotating direction (or circumferential direction) and a predetermined flexibility in the bending direction (or generally axial directions).
In the conventional flywheel assembly described above, the flywheel body is carried by the crankshaft only via the flexible plate. Therefore, it may rotate in an imbalance state when the flywheel itself is inclined with respect to its rotation axis due to bending forces.
A lower rigidity of the flexible plate can reduce the bending vibration more effectively. Particularly, it is possible to shift a resonance point from a practical operation region by reducing the rigidity of the flexible plate, and thereby noises during acceleration of the engine can be further reduced. However, the operation of a clutch usually requires a force to be exerted on the clutch assembly to disengage the clutch from transmitting torque. Typically, the disengaging force is applied in a direction that is ultimately exerted on the crankshaft of the engine. In other words, the disengaging force is generally axially oriented and is applied to a clutch assembly. The force, or release load, is then transmitted to the flywheel and the flex plate and further transmitted to the crankshaft of the flywheel. Consequently, if the rigidity of the flex plate in the axial or bending direction were excessively low, the flywheel would axially move toward the crankshaft an excessive extent during the clutch release operation, which would reduce a disengaging efficiency of the clutch.